1. Field of the Invention
The present invention relates to a magnetic resonance imaging apparatus and a method of setting a slice area.
2. Description of the Related Art
In a conventional method of setting a slice area for a magnetic resonance imaging apparatus, a tomographic image of an object is taken in advance as a positioning image, an operator sets a slice area for an actual scanning by arranging slice areas with respect to the positioning image displayed on a console (see, for example, JP-A 2003-290171 (KOKAI) or JP-A 2003-290172 (KOKAI)).
A magnetic resonance imaging apparatus generally excites hydrogen nuclei inside an object by irradiating the object placed in a static magnetic field with a radio frequency (RF) wave, and reconstructs an image from magnetic resonance signals emitted by the excitation of the hydrogen nuclei. However, a scan image may be degraded at a position far from the center of the static magnetic field because the static magnetic field becomes nonuniform with increasing distance from the center of the static magnetic field.
For this reason, if a scanning needs to be performed on an object across a wide range, the scanning is performed multiple times by moving a couch in the direction of the body axis of the object. In this case, the slice area needs to be set for each movement of the couch, and when setting the slice area using the positioning image, a rectangular parallelepiped range representing the slice area (hereinafter, “a volume”) is arranged to a position of the couch with respect to the positioning image. At this time, the operator arranges the volume in such a manner that a region of interest is included inside the volume by adjusting the position and the orientation inclination in accordance with a body part and a posture of the object.
However, for example, when performing angiography of a lower limb, there is a problem that an operation of setting the volume is cumbersome and complicated, because it is difficult to arrange the volume in such a manner that blood vessels in the region of interest completely fall within the volume. It is because that the angiography of the lower limb requires a wide range scanning, so that the scanning is performed multiple times, and furthermore, the lower limb cannot be stretched to a perfectly straight form and blood vessels inside the lower limb run three-dimensionally.